In that patent application there is disclosed a system for visualising internal human organs by means of an invasive ultrasonic technique.
In that system ultrasonic signals are generated and received by a transducer assembly mounted on the distal end of a catheter to be inserted into the patient. The present invention is concerned with the construction and manufacture of such a transducer arrangement and catheter.
The transducer arrangement of that earlier patent application consists essentially of a cylindrical array of piezo-electric crystal transducer elements. In the embodiment described in that earlier patent application, there are twelve such elements. Each element is discrete and is mounted in a groove formed in the circumference of a core member.
As explained in that earlier patent application, the degree of visual resolution obtainable depends upon the rate of signal output and resultant echo signal. This rate can be increased by increasing the number of transducer elements or alternatively by rotating a given number of transducer elements, as indicated in that earlier patent application.
There are clearly advantages and disadvantages associated with either attempting to increase the number of transducer elements in the case of a stationary transducer (i.e non-rotatable) and attempts to provide a drive arrangement for a rotatable transducer arrangement having fewer elements.
These difficulties are due to the very small scale involved in this type of transducer arrangement. Typically, the catheter at the end of which the transducer arrangement is mounted is less than 2.0 mm in diameter and typically 1.0 mm. It can thus be appreciated that the extremely small size of the transducer arrangement as a whole imposes limitations on the number of transducer elements which can be accommodated around the circumference. Equally, because of the very small scale involved, it is difficult to provide a rotatable transducer arrangement with an appropriate drive arrangement that can operate through tortuous vessels.
The present invention is concerned with improving the visual resolution referred to earlier by increasing the number of transducer elements beyond the maximum number which it had up to the present time been thought practicable in such a small scale arrangement.